RFR: 8338383: Implement JEP 491: Synchronize Virtual Threads without Pinning [v19]

[Patricio Chilano Mateo]

On Wed, 30 Oct 2024 00:52:32 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Patricio Chilano Mateo has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Add klass_name check for is_object_wait0
>>  - Fix comment in continuation.hpp
>
> src/hotspot/cpu/x86/interp_masm_x86.cpp line 361:
> 
>> 359:   // Make VM call. In case of preemption set last_pc to the one we want to resume to.
>> 360:   lea(rscratch1, resume_pc);
>> 361:   push(rscratch1);
> 
> Suggestion:
> 
>   push(rscratch1);  // call_VM_helper requires last_Java_pc for anchor to be at the top of the stack

Added it as a note with the comment above.

> src/hotspot/share/runtime/continuationFreezeThaw.cpp line 2045:
> 
>> 2043:     // If we don't thaw the top compiled frame too, after restoring the saved
>> 2044:     // registers back in Java, we would hit the return barrier to thaw one more
>> 2045:     // frame effectively overwritting the restored registers during that call.
> 
> Suggestion:
> 
>     // frame effectively overwriting the restored registers during that call.

Fixed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1823505700
PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1823511520